Photoinitiated Polymerization of 2-Hydroxyethyl Methacrylate by Riboflavin/Triethanolamine in Aqueous Solution: A Kinetic Study

Abstract

The polymerization of 1–3 M 2-hydroxyethyl methacrylate (HEMA) initiated by riboflavin/triethanolamine system has been studied in the pH range 6.0–9.0. An approximate measure of the kinetics of the reaction during the initial stages (~5% HEMA conversion) has been made to avoid the effect of any variations in the volume of the medium. The concentration of HEMA in polymerized solutions has been determined by a UV spectrophotometric method at 208 nm with a precision of ±3%. The initial rate of polymerization of HEMA follows apparent first-order kinetics and the rates increase with pH. This may be due to the presence of a labile proton on the hydroxyl group of HEMA. The second-order rate constants for the interaction of triethanolamine and HEMA lie in the range of 2.36 to 8.67 × 10−2 M−1 s−1 at pH 6.0–9.0 suggesting an increased activity with pH. An increase in the viscosity of HEMA solutions from 1 M to 3 M leads to a decrease in the rate of polymerization probably as a result of the decrease in the reactivity of the flavin triplet state. The effect of pH and viscosity of the medium on the rate of reaction has been evaluated.

Polymerization Assisted by Upconversion Nanoparticles under NIR Light

“…Here, we applied the endogenous, FDA-approved, non-toxic compound riboflavin in its water-soluble form flavin mononucleotide (FMN) as the photoinitiator for polymerization. Under UV and visible light, FMN was able to produce active radicals in the presence of the coinitiator triethanolamine (TEOHA) [31], which activates polymerization.…”

The selection of photoinitiators for photopolymerization of biodegradable polymers and its application in digital light processing additive manufacturing

“…For example, DMPA, TPO, and I2959 are type I photoinitiators, and the mechanism of initiation is homolytic cleavage process and forms radicals upon exposure to light radiation which is a more direct and fast kinetic reaction. 5 According to the studies of Oster et al and Ahmad et al, 25,26 B2 combined with TEOA is a type II photoinitiator. TEOA is the co-initiator that provides electrons to Vitamin B2 and prompts the formation of TEOA radicals.…”

Solvent Effect on Photoinitiator Reactivity in the Polymerization of 2-Hydroxyethyl Methacrylate

“…The RSD of the assay method is within ± 3%. The method has previously been used for the study of the photoinitiated polymerization of HEMA by RF/TEOHA system in aqueous solution [20].…”

“…Polymerization reactions of HEMA in water at 1, 2, and 3 M concentrations in the presence of different photoinitiators have shown that the rates are decreased with an increase in the viscosity of the medium [20]. In order to confirm the effect of medium viscosity on the rate of these reactions, the values of 𝑘 obs in organic solvents in the presence of RF were plotted as a function of the inverse of solvent viscosity (Table 1) and a linear relationship was observed as expected (Figure 3).…”